The use of implants to affix tissue grafts to bone is well known in the orthopedic arts. Common procedures in which such implants are used include, for example, the repair of rotator cuff tears, the repair of torn ligaments in the knee, among others. In these procedures, a socket is drilled or punched in the bone at the attachment site and a graft is secured to the bone using an implant placed in the socket. The graft may be secured to the implant by sutures, or, alternatively, an end of the graft may be placed in the socket and secured directly by an implant.
In rotator cuff repair, implants commonly referred to as “anchors” are used. These anchors occur in two types: conventional anchors in which the suture is passed through the cuff after anchor placement, and “knotless” anchors in which the suture is passed through the cuff prior to anchor placement. In the former case, the graft is secured in place by tying knots in the suture after it has been passed through the cuff so as to secure the cuff in the desired location. Conversely, as the name implies, when using a knotless anchor, the sutures are passed through the cuff and through a feature of the anchor such that when the anchor is inserted into the socket, the suture position is secured by the anchor. Accordingly, the tying of knots is not required. This is particularly advantageous when performing endoscopic (arthroscopic) repairs since the tying of knots arthroscopically through a small diameter cannula can be difficult for some surgeons and, moreover, there is an opportunity for tangling of the sutures.
Many anchors, both conventional and knotless, are supplied to the surgeon mounted on a driver—a device that the surgeon uses to place the anchor in the prepared socket in the bone. In the case of threaded anchors, the driver has a form like that of a screwdriver, and indeed functions in the same manner. The proximal portion of the device forms a handle that is grasped by the surgeon. Distal to the handle, an elongate distal portion has formed at its distal end features for transmitting torque to an implant. Some anchors, generally metallic anchors such as, for instance, the Revo® Suture Anchor by Conmed Corporation (Utica, N.Y.) and Ti-Screw Suture Anchor by Biomet Corporation (Warsaw, Ind.), have a protruding (male) proximal portion with a cross-section suitable for transmitting torque (typically hexagonal or square) and a transverse eyelet formed therein. The driver for such devices has a complimentary socket (female) formed in its distal end and a cannulation that extends from the interior of the socket to the proximal handle portion of the device. Sutures loaded into the eyelet of the anchor extend through the driver cannulation (or “lumen”) and are removably secured to the handle so as to retain the anchor in the socket of the driver. Such anchors are referred to in the orthopedic arts as “pre-loaded”, meaning that sutures come loaded into an anchor that is ready for placement by the surgeon using the associated driver.
Other threaded anchors have a socket (female) formed in their proximal ends. Once again, the socket has a cross-section suitable for transmitting torque that is typically polygonal, usually square or hexagonal. Typical of these are the V-LoX™ family of titanium suture anchors by Parcus Medical (Sarasota, Fla.) and the ALLthread™ anchors by Biomet Corporation (Warsaw, Ind.). The drivers for such devices have a protruding (male) torque-transmitting feature complementary to the socket (female) formed in the proximal end of the anchor. These drivers may be cannulated to accommodate sutures that are preloaded into the anchor in the manner previously described, with the sutures being either for the purpose of securing tissue after anchor placement, or for the purpose of removably securing the anchor to the driver, wherein the sutures are released from the driver after the anchor is placed in the bone and subsequently removed and discarded so as to allow removal of the driver from the anchor. The depth of the socket in the proximal end of the implant must be sufficient to enable transmission of the requisite torque needed for anchor placement without deforming or fracturing the implant. As the maximum depth of the torque-transmitting portion is generally limited only by the configuration of the anchor, it is considered to be matter of design choice. Indeed, the implant may have a cannulation that extends axially through the implant as well as a torque-transmitting cross-section forming a substantial proximal portion or the entirety of the implant's length. Implants of the Bio-Tenodesis Screw™ System by Arthrex, Inc have a cannulation with a constant torque-transmitting cross-section, and are used with a driver having a torque-transmitting portion that extends beyond the distal end of the anchor, wherein the portion of the driver extending beyond the anchor and a suture loop in the driver cannulation are used together to insert the end of a graft into a prepared socket prior to placement of the implant.
Knotless suture anchor fixation is a common way of repairing soft tissue that has been torn from bone. Illustrative examples of such “knotless” anchors include the Allthread™ Knotless Anchors by Biomet Incorporated (Warsaw, Ind.), the SwiveLock® Knotless Anchor system by Arthrex, Incorporated (Naples, Fla.), the HEALIX Knotless™ Anchors by Depuy/Mitek, Incorporated (Raynham, Mass.) and the Knotless Push-In Anchors such as the Knotless PEEK CF Anchor by Parcus Medical (Sarasota, Fla.). The procedure requires drilling or punching of holes into a properly prepared boney surface. After suture has been passed through soft tissue, the suture anchor is introduced into the socket and driven into the socket using a mallet or by screwing the anchor into the socket using a driver device. These driver devices typically resemble a screwdriver in form, having a proximal handle portion for applying torque or percussive force, and an elongate rigid distal portion having at its distal end a torque or percussive force-transmitting configuration. In the case of torque-transmitting drivers used with threaded anchors, the distal end of the driver typically has an elongate hexagonal or square distally extending portion that, through coupling with a lumen in the anchor having a complementary cross-section, transmits torque to the anchor. The lumen may extend through anchor so that the distal portion of the driver protrudes from the distal end of the anchor and rotates with the anchor during anchor placement.
Because the suture is drawn into the prepared socket along with the anchor during anchor placement, it is essential that a suitable length of suture extends between the graft and the anchor so that when the anchor is suitably positioned within the socket, the graft is properly positioned. Determining the proper length of suture to allow between the anchor and the graft so as to achieve optimal graft positioning is complicated since suture(s) may twist (a process referred to in the orthopedic arts as “suture spin”) during anchor placement, thereby shortening the effective length and changing the final graft position and/or undesirably increasing the suture tension.
U.S. Pat. No. 6,544,281 to ElAttrache et al. describes a cannulated anchor placement system having a rotating inner member (which acts as the driver) and a stationary outer member, wherein the rotating inner member serves to drive the threaded anchor. The rotating “driver” extends past the distal end of the anchor and is inserted into a prepared socket in the boney surface. A suture loop formed distal to the distal end of the driver “captures” or “secures” sutures attached to a graft or the graft itself to the distal end of the driver. The distal end of the driver is then inserted into the socket to a proper depth for anchor placement thereby drawing the graft to the desired position prior to placement of the anchor. The anchor is then threaded into the socket to the predetermined depth. This system constitutes an improvement over other commercially available alternatives. However, because the graft or sutures are secured to or pass through the distal end of the rotating inner (or “driver”), torque is transmitted not only to the anchor but also to the graft or sutures attached thereto by the suture loop. Accordingly, twisting of the sutures or graft frequently occurs, thereby changing the resulting suture tension and/or the graft position (a process referred to in the orthopedic arts as “graft shift”).
U.S. Pat. No. 8,663,279 by Burkhart et al. describes a knotless anchor system similar in construction to that of ElAttrache et al. A “swivel” implant having formed therein an eyelet is releasably and pivotably mounted to the distal end of a driver distal portion that extends distally beyond the distal end of an anchor. After sutures are passed through the graft, they are threaded into the eyelet of the swivel implant at the distal end of the driver. The distal end of the driver with the swivel implant is then inserted into the socket. By pulling on the suture tails, the graft is moved into position and secured by screwing the anchor into the socket. However, because the sutures/graft are secured to the driver by means of the swivel eyelet implant, the torque that may be transmitted to the sutures/graft is limited. However, torque transmission is not eliminated since the swivel implant is retained in the driver distal end by a suture loop under tension, which extends through the cannula of the driver to the driver's proximal end where the suture ends are cleated. While an improvement over the ElAttrache anchor system, suture spin is not eliminated in all cases, and indeed, cannot be since the suture-retaining implant is mounted to the driver, which rotates during anchor placement. As such, some level of torque transmission due to friction between the driver distal end and the swivel eyelet implant is inevitable.
Other knotless anchors such as the ReelX STT™ Knotless Anchor System by Stryker® Corporation (Kalamazoo, Mich.) and PopLok® Knotless Anchors by ConMed Corporation (Utica, N.Y.) have complex constructions and require that the surgeon perform a sequence of steps to achieve a successful anchor placement with the desired suture tension and proper cuff position. The sequence of steps adds to procedure time and creates opportunities for failure of the placement procedure if a step is not performed properly.
Accordingly, there is a need in the orthopedic arts for a knotless anchor system that allows the surgeon to establish the graft position, and, while maintaining that position, place the anchor without changing the suture tension or causing a shift in the graft position due to suture spin. Furthermore, if the anchor is threaded, placement of the anchor in the socket must occur without spinning of the suture.
If a graft such as a biceps tendon is directly affixed to a bone by insertion of the graft into a socket (a technique referred to in the art as “bio-tenodesis”), it is essential that the graft be fully inserted so as to be engaged by the full length of the implant. It is also important that the position of the graft be maintained during anchor insertion. Further, it is essential that the alignment of the implant (referred to in this case as an “interference screw”) be coaxial, or if slightly shifted, parallel to the axis of the socket. It is also desirable that the sutures used to draw the graft into the socket do not spin or twist during anchor placement as this may change the position and tension of the graft from that intended by the surgeon. In sum, there is a also need in the suture arts for an interference screw and implant placement system in which graft position within the socket is maintained throughout the implant placement process, and in which suture spin or twisting is prevented.
Improved implant systems can also find utility in the context of spinal fusion surgery, wherein rigid posterior or lateral or anterior elements, either pedicle based, interbody based, or vertebral body based, or posterior element based, are routinely performed, by the placement of screws into the bony spinal elements and, through either internal mechanisms or rigid bridging devices, engage into adjacent bony elements or interspaced to provide rigid fixation. Illustrative examples of commercially available spinal fixation devices include, for example, Synthes (Raynham, Mass.), Nuvasive (San Diego, Calif.) and Amendia (Atlanta, Ga.), devices that interlock cervical, thoracic or lumbar or sacral levels to rigidly prevent movement and fuse or allow for fusion of diseased or degenerated segments of spine to prevent painful or disabling movement. These rigid zones of fixation create zones above and below these constructs, which are known as junctional or transitional zones or levels. There is need in the art for a bracing mechanism that can disperse load from the rigidly fixed spinal segments having undergone prior fusion or fixation, to unfused adjacent spinal segments. Such a bracing device, while not providing absolute rigid fixation but allowing for movement, would provide for bracing of the non fused segments while off-loading or reducing the forces that, prior to the application of such a device, would have been entirely borne by the intervertebral discs and adjacent bony elements and ligaments adjacent to the prior rigid fixed segments. It is this increased force that is postulated to result in failure of the adjacent segment.
Suitable bracing devices can be inserted either along the anterior aspect of the spinal segments, the posterior aspect of the spinal segments, or between spinal segments. Between these anchor devices and the spinal segments or between the fusion devices and spinal segments, or bridging these spinal segments and fusion devices to intact spinal segments, either soft tissue in the form of grafts, or with braided suture constructs, or with a combination thereof, bone anchors are utilized to insert these tension bearing or tension off loading constructs. Such tension-bearing constructs serve to provide a dynamic rather that rigid transition from the fused spinal segments to the adjacent spinal segments. The purposes of theses constructs are to reduce the load applied to the intervertebral discs above and below the fused spinal segments. This transitional loading allows the adjacent musculature to recover following spinal fusion surgery while protecting the discs until the muscle has recovered sufficiently, while also allowing needed movement at the transitional levels so as to not have created another static or rigidly fixed level. In addition, such constructs can be utilized to reconstruct spinal ligaments. Such reconstructions can be performed either independent of, or in addition to rigid spinal fixation or along with intervertebral body disc replacements to help restore normal spinal segment mobility and preserve or protect the constructs.